1. Field of the Invention
The present disclosure relates to a liquid crystal display device, and more particularly, to a method of fabricating a lightweight and thin liquid crystal display (LCD) device using a glass substrate having a thickness of about 0.1t (millimeter) to about 0.5t .
2. Discussion of the Related Art
Recently, as society has entered in earnest into the information age, the field of display devices that represent all sorts of electrical signals as visual images has developed rapidly. Particularly, since the LCD device has characteristics of light weight, thinness and low power consumption, the LCD device has been widely used as a substitute for a display device of cathode-ray tube type.
A related art liquid crystal display (LCD) device uses optical anisotropy and polarization properties of liquid crystal molecules. The liquid crystal molecules have a definite alignment direction as a result of their thin and long shapes. The alignment direction of the liquid crystal molecules can be controlled by applying an electric field across the liquid crystal molecules. In other words, as the intensity or direction of the electric field is changed, the alignment of the liquid crystal molecules also changes. The LCD device includes a liquid crystal panel is formed by attaching an array substrate including a pixel electrode and a color filter substrate including a common electrode. The alignment direction of the liquid crystal molecules in a liquid crystal layer between the array substrate and the color filter substrate is controlled by an electric field, which is generated between the pixel and common electrodes, such that images can be displayed by controlling light transmissivity.
Since an active matrix LCD (AM-LCD) device has excellent characteristics of high resolution and displaying moving images, the AM-LCD device has been widely used. Particularly, the LCD device including a thin film transistor (TFT) as a switching element is referred to as a thin film transistor LCD (TFT-LCD) device.
FIG. 1 is an exploded perspective view of a related art liquid crystal panel. As shown in FIG. 1, the liquid crystal panel includes an array substrate 10, a color filter substrate 20, and a liquid crystal layer 30. The array substrate 10 and the color filter substrate 20 face each other, and The liquid crystal layer 30 is interposed therebetween.
The array substrate 10 includes a first substrate 12, a gate line 14, a data line 16, a thin film transistor (TFT) Tr, and a pixel electrode 18. The gate and data lines 14 and 16 are formed on the first substrate 12 and cross each other to define a pixel region P. The TFT Tr is formed at a crossing portion of the gate and data lines 14 and 16. The pixel electrode 18 is formed in the pixel region P and connected to the TFT T.
The color filter substrate 20 includes a second substrate 22, a black matrix 25, a color filter layer 26, and a common electrode 28. The black matrix 25 is formed on the second substrate 22 and has a lattice shape. The black matrix 25 corresponds to a non-display region of the first substrate 12. The non-display region of the first substrate 12 includes the gate and data lines 14 and 16 and the TFT T. The color filter layer 26 corresponds to the pixel region P and includes red, green and blue color filter patterns 26a, 26b and 26c. The common electrode 28 is formed on the black matrix 25 and the color filter layer 26. The common electrode 28 generates an electric field with the pixel electrode 18 such that the liquid crystal layer 30 is driven by the electric field.
Although not shown, a seal pattern is formed along edges of the first and second substrates 12 and 22. The seal pattern prevents the liquid crystal layer 30 overflowing. In addition, first and second alignment layers may be formed between the first substrate 12 and the liquid crystal layer 30 and between the second substrate 22 and the liquid crystal layer 30. First and second polarization plates may be formed on an outer surface of one of the first and second substrates 12 and 22.
A backlight assembly is formed on a rear side of the first substrate 12 to apply light into the liquid crystal panel. When a scan signal is applied to the TFT Tr through the gate line 14 to turn on the TFT Tr, an image signal is applied to the pixel electrode 18 through the data line 16 such that an electric field is generated between the pixel electrode 18 and the common electrode 28. As a result, the liquid crystal molecules in the liquid crystal layer 30 are driven by the electric field to display images.
Generally, a glass plate having transparent and insulating properties is used for the first and second substrates 12 and 22. Namely, a plurality of processes are conducted to form an array element and a color filter element are formed on the glass substrate. Unfortunately, the glass substrate is drooped, cracked or broken during the process or transport between the processes.
To prevent or minimize possibility of drooping, cracking or breaking problem, the glass substrate having an enough thickness of about 0.7t is used. However, the liquid crystal panel, which is fabricated using the 0.7t thickness glass substrate, is relatively heavy and thick such that there is a difficulty to produce a lightweight and thin LCD device. Particularly, with personal potable terminals such as a notebook computer, a personal digital assistant (PDA), the LCD device for the terminals is increasingly required to be lightweight and thin.
Accordingly, before attaching the first and second polarizing plates on the liquid crystal panel, the glass substrate of the liquid crystal panel is exposed to hydrofluoric (HF) solution and an outer side of the array substrate and the color filter substrate is etched such that the glass substrate for the array substrate and the color filter substrate has a thickness below about 0.5t .
However, as shown in FIG. 2, which is a schematic view illustrating an etching process of an outer side of the liquid crystal panel, the hydrofluoric solution is sprayed onto the both outer sides of the liquid crystal panel 50 using an etchant spray apparatus 90 such that an outer side of each of the array substrate 10 and the color filter substrate 20 is etched. Unfortunately, since an entire surface of the glass substrate is not uniformly etched, there are fine griffith flaws or concaves on an outer surface of the array substrate 10 and the color filter substrate 20 such that roughness is increased.
When the first and second polarizing plates are attached to the outer sides of the liquid crystal panel 50 having increased roughness, an adhesive property is reduced. In addition, since a portion of the concaves is thinner than other portions, strength of the glass substrate is weakened or reduced. Particularly, tensile strength is concentrated at the concaves such that cracks are generated and the glass substrate is broken.
In addition, since the etching process for the glass substrate with the HF solution is required ten to several tens minutes, production yield is reduced.
Moreover, 0.7t thickness glass substrate is more expensive than 0.5t thickness glass substrate. To produce the LCD device including 0.5t glass substrates by etching 0.7t glass substrates after producing the liquid crystal panel with 0.7t glass substrates is very inefficient in sides of cost and a fabricating processes.
Since costs of the etching process is about 55% of the production costs of the glass substrate (0.7t glass substrate cost+etching process cost), the LCD device loses price competitiveness because of the etching process.